Physiological adaptations to resistance training in rats selectively bred for low and high response to aerobic exercise training

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Authors

  • Juha P Ahtiainen
  • Sanna Lensu
  • Ilona Ruotsalainen
  • Moritz Schumann
  • Johanna K Ihalainen
  • Vasco Fachada
  • Christopher L Mendias
  • Matthew S Brook
  • Kenneth Smith
  • Philip J Atherton
  • Lauren G Koch
  • Steven L Britton
  • Heikki Kainulainen

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NEW FINDINGS: What is the central question of this study? Can phenotypic traits associated with low response to one mode of training be extrapolated to other exercise-inducible phenotypes? The present study investigated whether the low responder rats to endurance training are also low responders for resistance training. What is the main finding and its importance? By resistance training, high responder rats to aerobic exercise training (HRT) improved more maximal strength compared to the low responder rats (LRT). However, greater gains in strength in HRT was not accompanied with muscle hypertrophy suggesting that these responses observed could be mainly of neural origin.

ABSTRACT: The purpose of this study was to determine whether rats selectively bred for low and high response to aerobic exercise training cosegregate for differences in muscle adaptations to ladder climb resistance training. Five high responder (HRT) and five low responder (LRT) rats completed the resistance training while six HRT and six LRT rats served as sedentary controls. Before and after the 6-week intervention, body composition was determined by DXA. Before tissue harvesting, right triceps surae muscles were loaded by electrical stimulation. Muscle fiber cross-sectional areas, nuclei per cell, phosphorylation status of selected signaling proteins of mTOR and Smad pathways, and muscle protein, DNA, and RNA concentrations were determined for the right gastrocnemius muscle. Daily protein synthesis rate was determined by deuterium oxide (D2 O) method from the left quadriceps femoris muscle. Tissue weights of leg and arm muscles were measured. In response to resistance training, maximal carrying capacity was greater in HRT (∼3.3 times per body mass) than LRT (∼2.5 times body mass), indicating greater improvements of strength in HRT. However, muscle hypertrophy that could be related to greater strength gains in HRT was not observed. Furthermore, noteworthy changes within the experimental groups or differences between groups were not observed in the present measures. Lack of hypertrophic muscular adaptations despite considerable increases in muscular strength suggest that adaptations to the present ladder climb training in HRT and LRT rats were largely induced by neural adaptations. This article is protected by copyright. All rights reserved.

Original languageEnglish
JournalExperimental physiology
Number of pages37
DOIs
Publication statusPublished - 05.09.2018

ID: 3489696

DOI

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